Tape recorder
Since some early refinements improved the fidelity of the reproduced sound, magnetic tape has been the highest quality analog recording medium available.
The wax strip passed from one eight-inch reel around the periphery of a pulley (with guide flanges) mounted above the V-pulleys on the main vertical shaft, where it came in contact with either its recording or playback stylus.
In playback mode, a dull, loosely mounted stylus, attached to a rubber diaphragm, carried the reproduced sounds through an ear tube to its listener.
The tapes and machine created by Bell's associates, examined at one of the Smithsonian Institution's museums, became brittle, and the heavy paper reels warped.
The audio signal could be immediately replayed from the same recorder unit, which also contained photoelectric sensors, somewhat similar to the various sound-on-film technologies of the era.
A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal to be amplified and played back through a loudspeaker.
The BBC installed a Blattnerphone at Avenue House in September 1930 for tests, and used it to record King George V's speech at the opening of the India Round Table Conference on 12 November 1930.
[19][20] In 1933, the Marconi Company purchased the rights to the Blattnerphone, and newly developed Marconi-Stille recorders were installed in the BBC's Maida Vale Studios in March 1935.
[22] Despite these drawbacks, the ability to make replayable recordings proved useful, and even with subsequent methods coming into use (direct-cut discs[23] and Philips-Miller optical film[24] the Marconi-Stilles remained in use until the late 1940s.
[25] Magnetic tape recording as we know it today was developed in Germany during the 1930s at BASF (then part of the chemical giant IG Farben) and AEG in cooperation with the state radio RRG.
Walter Weber, working for Hans Joachim von Braunmühl [de] at the RRG, discovered the AC biasing technique, which radically improved sound quality.
[26] During World War II, the Allies noticed that certain German officials were making radio broadcasts from multiple time zones almost simultaneously.
[a] In the final stages of the war in Europe, the Allies' capture of a number of German Magnetophon recorders from Radio Luxembourg aroused great interest.
[28][citation needed] American audio engineer John T. Mullin and entertainer Bing Crosby were key players in the commercial development of magnetic tape.
Mullin's unit soon amassed a collection of hundreds of low-quality magnetic dictating machines, but it was a chance visit to a studio at Bad Nauheim near Frankfurt while investigating radio beam rumors, that yielded the real prize.
[citation needed] Mullin gave two public demonstrations of his machines, and they caused a sensation among American audio professionals; many listeners literally could not believe that what they heard was not a live performance.
By luck, Mullin's second demonstration was held at MGM Studios in Hollywood and in the audience that day was Bing Crosby's technical director, Murdo Mackenzie.
[26] Bing Crosby, a top movie and singing star, was stunned by the amazing sound quality and instantly saw the huge commercial potential of the new machines.
Crosby disliked the regimentation of live broadcasts 39 weeks a year,[26] preferring the recording studio's relaxed atmosphere and ability to retain the best parts of a performance.
He asked NBC to let him pre-record his 1944–45 series on transcription discs, but the network refused, so Crosby withdrew from live radio for a year.
Mullin was asked to tape one show as a test and was subsequently hired as Crosby's chief engineer to pre-record the rest of the series.
[citation needed] The BBC acquired some Magnetophon machines in 1946 on an experimental basis, and they were used in the early stages of the new Third Programme to record and play back performances of operas from Germany.
1+7⁄8 in/s (4.8 cm/s) and occasionally even 15⁄16 in/s (2.4 cm/s) were used for voice, dictation, and applications where very long recording times were needed, such as logging police and fire department calls.
[citation needed] The 8-track tape standard, developed by Bill Lear in the mid-1960s, popularized consumer audio playback in automobiles in the USA.
[32][failed verification] The development of Dolby noise reduction technology in the 1960s brought audiophile-quality recording to the Compact Cassette also contributing to its popularity.
[citation needed] Since their first introduction, analog tape recorders have experienced a long series of progressive developments resulting in increased sound quality, convenience, and versatility.
[citation needed] Due to electromagnetism, electric current flowing in the coils of the tape head creates a fluctuating magnetic field.
This causes the magnetic material on the tape, which is moving past and in contact with the head, to align in a manner proportional to the original signal.
In particular, the granular nature of the magnetic material adds high-frequency noise to the signal, generally referred to as tape hiss.
Tape made possible the first sound recordings totally created by electronic means, opening the way for the bold sonic experiments of the Musique Concrète school and avant-garde composers like Karlheinz Stockhausen, which in turn led to the innovative pop music studio-as-an-instrument recordings of artists such as Frank Zappa, the Beatles, and the Beach Boys.
